Manufacturing method for semiconductor substrate, manufacturing method for liquid ejection head, semiconductor substrate, and liquid ejection head

A method for manufacturing a semiconductor substrate that includes, on a substrate, a first electrode, a second electrode, a first electrode pad connected to the first electrode via a first connection portion, and a second electrode pad connected to the second electrode via a second connection portion, the method comprising:

• forming the first electrode, the first connection portion, and the second connection portion from a third metal film;
• forming the second electrode from a fourth metal film having a standard electrode potential higher than that of the third metal film;
• forming a second metal film, having a standard electrode potential lower than that of the third metal film, in a region including the first electrode, the second electrode, the first connection portion, and the second connection portion;
• forming a first metal film, having a standard electrode potential higher than that of the second metal film, on the second metal film;
• and
• forming the first electrode pad and the second electrode pad by patterning the first metal film and the second metal film,
• wherein, during the forming the first electrode pad and the second electrode pad, the first electrode, the second electrode, the first electrode pad, and the second electrode pad are exposed to an electrolyte.

A semiconductor substrate comprising:

• on a substrate, a first electrode, a second electrode, a first electrode pad connected to the first electrode via a first connection portion, and a second electrode pad connected to the second electrode via a second connection portion,
• wherein each of the first electrode pad and the second electrode pad includes a first metal film, and a second metal film that is in contact with the first connection portion or the second connection portion and has a standard electrode potential lower than that of the first metal film,
• wherein each of the first electrode, the second electrode, the first connection portion, and the second connection portion includes a third metal film having a standard electrode potential higher than that of the first metal film,
• wherein S2/S1>1
• where S1 is an exposed area of the first electrode, and S2 is an exposed area of the second electrode in the first electrode, the second electrode, the first electrode pad, and the second electrode pad, and
• wherein W2/W1>1
• where W1 is an undercut width of the second metal film with respect to an end of the first metal film of the first electrode pad in a direction parallel to a surface of the substrate, and W2 is an undercut width of the second metal film with respect to the end of the first metal film of the first electrode pad.